Review of 2007 Toyota Prius

The Prius is a really some kind of futuristic flying saucer cunningly
disguised to look like a car. Warp this baby back to 1980 and the natives
wouldn't be able to fix it. Heck, you can't even push it if the
batteries die. For instance:
- it doesn't have a regular engine, it has two 3-phase AC motor-generators
powered by a liquid-cooled inverter and voltage booster.
- it has a nickel-metal-hydride battery with temperature sensors and
a computer-controlled ventilation system
- it has touch-screen controls for the climate-control
and audio systems,
like the 767 airliner
- it has a fly-by-wire control system like a military jet, with yaw sensors and an optional gyrocompass
- it has an aerodynamic resistance coefficient of 0.26, achieved
with things like underbody panels and
air dams around the wheels
- it doesn't have an ignition switch, it has a power button and an electronic immobilizer
key. With the optional "smart key", you don't even have to remove it from your pocket
to drive
- it continues to operate under computer control even when supposedly "turned off",
running pumps and ventilation systems autonomously

Why Prius ?

We were looking for something with significantly better fuel economy
and lower emissions than a regular car. In the current Canadian market, that
means a hybrid. There seem to be no viable battery/electric or fuel cell
cars available at this time.

Many car manufacturers are still advertising how powerful their cars
are, or how fast, or how well they perform on winding highways with no other
cars in sight. As if most drivers ever see roads like that (OK, the
Duffy Lake road is pretty neat).

The Prius, on the other hand, is great for real life - being stuck in traffic.
The gasoline engine cuts out, and it will creep forward quietly on
battery power with zero emissions. Or, with the EV button (standard in Europe,
for North America see here
or google "Prius EV mod"), you can maybe make it to the corner store on battery alone.
(don't bother; the EV switch is a gimmick - good for backing the car out to wash it, or sneaking across
the mall car park from the drugstore stalls to the bank stalls. The lights still come on, so it's not
quite "stealth")

Essentially, the Prius has a
gasoline engine and two electric motor-generators
connected to a planetary gear system which drives the front wheels.
Electric power is provided from a 200V NiMh battery via a fluid-cooled inverter.
The motor-generators provide regenerative braking, 100% of the power in reverse, and
extra power for acceleration. The Prius doesn't actually have any gears in the normal sense;
the gasoline engine normally runs at a fuel-efficient low-emission rpm and one of the motor-generators
adjusts the torque on the other end of the planetary gear to give the desired road speed. Think
of a normal car with the left driving wheel spinning on ice and the right one stationary - by braking the left
wheel you could transfer some torque to the right one to move forward. (Later) - I realize now that
the preceding sentence is rubbish, at least the bit about always running at an efficient RPM. From the RPM-speed
graph further down, it is clear the engine RPM is all over the place. It does spend a fair bit of time
at about 1300 RPM, though, which is probably the battery-charging regime.

It is not possible - at least, in the
factory-standard model - to charge the NiMH battery in any other way, so you are
still dependant on gasoline, though Hymotion makes a conversion kit.

A small 12V lead-acid battery provides power to run the computers, lights,
and control systems. It is recharged from the HV system via a DC-DC
converter. As far as I can determine, it cannot be used to start the car; the motor-generator
is needed for that, powered by the high-voltage battery. But if it runs flat the door locks
won't work. (Since the 12V battery is in the back, which won't open without power, you have to
connect jump cables to the fuse box next to the engine)

Performance

Pretty good, IMO. OK, it's not going to win drag races or tow a 2000kg boat, but it did OK on
our trip across the mountains, taking the grades without gasping for breath
and overtaking most everything on the road (100kph limit, and 30k over risks a ticket for
dangerous driving, so it's no autobahn...). The stock tires are a bit iffy on ice, though.

Easter Egg

Holding the "Info" button down on the centre console while turning the lights on and off brings up
a diagnostic display.

Road Trip

About 1720 km through the Rockies from Vancouver to Prince George and
back, plotting energy consumption against elevation: PG.html

Fuel Consumption

The book says something like 4.7 l/100km. We get about 5.0 in the city, maybe 4.7 on the highway. The tank
is smaller than average, and I think we get about 500km/tank. For comparison, our Toyota Previa (4cyl AWD minivan)
gets about 13 l/100km, and my 200cc motorcycle 2.8.

August 2008. Drove (4 passengers, luggage, frame tent, stove, cooler etc.)
from Vancouver to La Jolla (near the Mexican border)
via Las Vegas, San Francisco, Death Valley, Anaheim (not necessarily in that order).
The air conditioning held 23C inside with 45C outside - pretty impressive.
Ran out of gas on I5 and all sorts of warning lights came on ("take to dealer").
Battery got us to a rest area where I bought some gas from an ATV owner
(thanks!) and all the warnings disappeared.
Long steep grades in the US Rockies used up the battery more than trips
in the Canadian Rockies. The battery indicator was nearly on zero
and I guess we had less power available than normal, but this was on
really twisty roads and we couldn't have used it anyway. When stopping
after a long climb, I let
the engine run awhile to recharge the 500V battery (really don't want to
be unable to start the engine; there is no possibility of a jump start,
unless off another Prius whose owner doesn't mind voiding the warranty)

Sept. 2008. Bought a hitch kit to support a bicycle carrier. There's lots of
these now; they all look much the same and bolt on to body in place
of the tie-down brackets. You have to cut the plastic underbody cover
somewhat.